Question

given the sequence, identify the $a_1$ and the common difference:
30, 39, 48, 57....
options:
$a_1 = 30; d = 9$
$a_1 = 39; d = 57$
$a_1 = 30; d = -9$
$a_1 = 57; d = 48$

Explanation:

Step1: Identify first term $a_1$

The first term of the sequence 30, 39, 48, 57... is the first number, so $a_1 = 30$.

Step2: Calculate common difference $d$

Subtract consecutive terms: $d = 39 - 30 = 9$, or $48 - 39 = 9$, or $57 - 48 = 9$.

Answer:

$a_1 = 30; d = 9$